1. Field of the Invention
This invention relates to a mobile communications system wherein a plurality of radio base stations can communicate with each other by way of a common mobile exchange and each of the radio base stations can communicate with a plurality of mobile stations within a service area by wireless, communications and more particularly to a group communications method for a mobile communications system of the type mentioned wherein different mobile stations in different service areas can communicate with each other by group communications.
2. Description of the Related Art
A group communications method for a mobile communications system of the type mentioned is conventionally known and disclosed, for example, in Japanese Patent Laid-Open Application No. Heisei 5-22220, wherein group communications can be performed by a paging function from a mobile exchange only when a sending side mobile station which belongs to the same group as receiving side mobile stations is present within a same service area as the receiving side mobile stations.
In particular, the mobile exchange transmits a paging signal only to one radio base station which has received a call out signal from a sending side mobile station and has a service area in which the sending side mobile station is present, and searches out and calls receiving side mobile stations of a same group as that of the sending side mobile station only within the service area of the one radio base station. Consequently, when a receiving side mobile station or stations are present in the service area of a different ratio base station from that of the sending side mobile station, group communications cannot be performed.